Electric windshield wiper



Aug. 29, 1944. J. BWHlTTED ELECTRIC WIND SHIELD WIPER 3 Sheets-Sheet 1Filed April 2. 1941 ZN W 9, 1944. J. B. WHITTED v 21,357,152

. I ELECTRIC WIND SHIELD WIPER Filed April 2, 1941 3 Sheets-Sheet 2 j uzAug. 29, 1944. I J. B. WHITTED ELECTRIC WIND SHIELD WIPER Filed April 2,1941 s Sheets-Sheet 5 Pmmd Aug. 29, 1944 John B. Whitted, Glencoe, lll.,acsignor to Stewart-Warner Corporation, Chicago, Ill., a corporation ofApplication April 2, 1941, Serial No. 386,496

('01. Hie-253) 11 Claims.

My invention relates generally to electrical windshield wipers and moreparticularly to electrical windshield wipers of the kind commonly usedon automobiles.

When an electric windshield wiper is turned oif, it is essential thatthe wiper blades automatically come to rest in a predetermined parkedposition out of the line of the operator's vision.

In addition, it is desirable that a windshield wiper be constructed assimply and economically as possible in order to minimize its cost eitheras original equipment or as a replacement part for automobiles.

It is an object of my invention to provide an electric windshield wiperwhich stops the wiper blades automatically in a predetermined positionso as not to obstruct the driver's vision.

' A further object of my invention is to provide an electric windshieldwiper having a small nu-mber of moving parts.

Another object is to provide an improved stopping and parking mechanismfor electric windshield wipers.

A further object of my invention is to provide an electric windshieldwiper which is simple in construction and operation and which iseconomical to manufacture.

Other objects and advantages of the invention will appear from thefollwowing description.

In the drawings:

Fig. 1 is a diagrammatic view showing my invention applied to thewindshield of an automobile. The horizontal position of the blades isindicatedby full lines while the vertical position is indicated bybroken lines;

Fig. 2 is a side elevation of the driving mechanism;

Fig. 3 is an end view of the driving mechanism taken on the line 3-3 ofFig. 2;

Fig. 4 is a generally vertical section taken on the line 44 of Fig. 3;

Fig. 5 is a sectional view taken on the line 5--5 of Fig. 4;

Fig. 6 is a vertical section taken on the line 66 of Fig. 5;

Fig. '7 is a transverse section taken on the line 1-4 of Fig. 4;

Fig. 8 is an irregular transverse section taken on the line 8-8 of Fig.6; Fig. 9 is a detailed sectional view taken on the line 9-9 of ,Fig. 6;

Fig. 10 is a wiring diagram;

Fig. 11 is a sectional view of a. modification of. the coupling membershown in Fig. 4; and

Fig. 12 is a plan view of one end of the coupling member shown in Fig.11.

Referring to Fig. 1, the motor 20, the driving mechanism 22. and thelinkage 24 for the wiper blades 25 are mounted upon a support 26 locatedbeneath the cowling of the automobile, and

below the windshield 26. Vibration created by the motor and other movingparts is dampened by means of a rubber cushion 36.

The driving mechanism, as in Fig. 4, is encased in a compound housing 32having a flange 34 to. which is attached the motor 20. Within thishousing is a worm wheel 36 turned by a. worm gear 36 which is coupled tothe armature shaft 46 of the motor.

Armature shafts in inexpensive motors of the type used in electricwindshield wipers are seldom uniform in length. To compensate for thisvariation I employ a novel coupling 42 to join the armature shaft 46 andthe worm gear shaft 44. This coupling 42 has at one end thereof aball.46 through which extends a pin 48, and has at the other end thereofapln 56 alone. The worm gear shaft 44 is provided with an axial bore 52and opposed axial slots 54 in which are movably mounted respectively theaforementioned ball 46 and pin 48. A second ball 56 which ispress-fitted into the bore 52 of the worm gear shaft serves as a bearingsurface for the ball 46 and thus prevents the pin 48 from touching theinner ends of the slots 54.

The armature shaft 46 is likewise bored to accommodate the other end 58of the coupling 42 and is provided with slots which carry the pin 56. Aspring 62 in the bore 64 of the armature shaft urges a washer 66 againstthe end 58 of the coupling 42 thus holding the coupling securely inplace and taking up any end play that may be present due to'variation inthe length of the armature shaft.

From the'foregoing description it may be seen that the coupling 42 notonly compensates for differences in the length of the armature shaftbutalso serves as a universal joint, and s0 makes it unnecessary for themotor and the worm gear to be in precise axial alignment.

The worm gear shaft 44 is journaled in bushings 68, 10 and is providedwith grease return grooves 12 which prevent the escape of lubricant fromthe gear housing. The axial thrust of the worm gear is exerted in thedirection of a ball 14 which is press-fitted into the other bored end I6of the worm gear shaft and which protrudes slightly therefrom. The ball14 gears against a thrust plate I8 which is securely staked into placeagainst an annular shoulder 86.

That portion of the housing 32 which contains the worm wheel 36 issealed by means of a gasket 82 and a cover plate 84. This cover plate isextended to serve as a mounting 86 for the entire driving mechanism, andis attached through the rubber cushion 3|! to the support 26 (see Fig.2).

One end 68 of the worm wheel shaft 89 is journaled in a short bushing 96which is pressed into an extension 92 of the housing 32. The extend- 2naled in an elongated bushing 88 which protrudes through the cover plate84 and which is firmly attached theretoby pressing.

A combined cranking and camming member 08 is pressed upon and riveted tothe extending end 84 of the worm wheel shaft 89. This combination memberincludes both a crank pin I which is linked to the windshield wiperblades, and a camming surface I 02 which actuates an insulatedbutton-shaped cam follower I04.

The cam follower I04 which is part of an electrical make and breaksystem for the motor 20 extends through a hump I08 in the housing 32 andis held in place by a spring arm I08. The reciprocating motion of thecam follower is transmitted to the spring arm. I08 which has a contactIIO riveted thereon. vA second spring arm II2 has a'contact II4 whichco-operates with the contact I I0 to make or break the motor circuitwhen the spring arm I08 is flexed by the cam follower I04. Both springarms are dog-leg shaped in order to provide clearance for the worm gearshaft 44, and are riveted to a semicircular fibre insulator II8positioned within the housing by means of bosses 8, I20, I22 (see Fig.7). The rivets I24, I28 which hold the spring arms extend throughenlarged holes I28 in the housing and are staked and soldered tocontacts I 30, I32 mounted on a second fibre insulator I 34 on theoutside of the housing. This method of mounting the parts of the makeand break system prevents them from being grounded by the housing 32(See Fig. 9).

The motor circuit established by the contacts H0, H4 of the make andbreak system is in parallel with the principal motor circuit which iscontrolled by a manual switch I 38 (see Fig. 10). Therefore, when acircuit to the motor 20 is established by the manual switch, the motorwill operate whether or not current passes through the make and breaksystem. It follows that if the circuit is broken by the manual switch,the motor will continue to operate until the contacts IIO, II 4 areseparated by the cam follower I 04. If a two speed manual switch is usedin connection with my windshield wiper, it is advisable to connect thecontacts II 0, H4 with the =low speed circuit in order to diminish thespeed of the motor before stopping it. This will assure proper operationof my novel braking mechanism.

This braking mechanism comprises in part a braking cam I38 constructedof sheet metal or similar material and having a braking incline I40, aflat dwell I42 at the top thereof, and a reverse slope I 44, The brakingcam I38 is pressed into holes I48 in the side of the worm wheel 38adjacent its circumference.

- A brake shoe I48 in the form of a stationary V-shaped camming membercomprises the other part of the braking mechanism. The brake shoe I 48which is formed integral with a leaf spring I50 has both a brakingsurface I52 which is shaped complementary to the incline I40 of thebraking cam I38, and a reverse incline I54 which is shaped complementaryto the reverse slope I44 of the braking cam I38. These surfaces I52, I54meet at an apex I58,

The leaf spring I50 which carries the brake shoe I48 is affixed by meansof rivets I58 to the inner side of the cover plate 84 ]and is centrallyapertured I80 in order that the shaft 89 of the worm wheel 38 may passtherethrough.

The braking cam I38 and the brake shoe I 48 are relatively positioned sothat, with 3. 8. EY-

oiution 0f the worm wheel 38, the braking incline I of the braking camI38 will meet the braking surface I82 of the brake shoe. When the motor20 is running, it has sumcie'ntpower to flex the leaf spring I and causethe brakingcam I88 to override the brake shoe I48. On the other hand,when the current to the motor 20 is cut om'the leaf spring I50 issufliciently rigid to hold the brake shoe I48 against the slowly movingbrakingcam, I 38 sothat the braking surface I52 of the brake shoe bearsagainst the braking incline I40 thereby stopping the entire wipermechanism in its parked position. Most of the braking effort is exertedby the brake shoe I48 during the time that the apex I58 is on theincline side of the braking cam I38, although some braking effort may beexerted by'the contact of the apex I58 with the fiat dwell Inc: thebraking cam should the worm wheel. 38 occasionally move to that positionbefore stopping.

Parking the wiper blades in .-a' "predetermined position is dependentupon the relative arrangement of the operative parts of the entirewindshield wiper assembly. It is necessary, therefore, to locate thebraking cam I88 at a point on the worm wheel 38 which will permit thebraking cam and the brake shoe I48 to meet momentarily after the circuitto the motor 20 is broken by the action of the camming surface I02 uponthe cam follower I04 with the resulting separation of the contacts IIO,II 4 (the circuit through the manuai switch I38 having been brokenpreviously). The crank pin I00 to which is linked the wiper blades 25,must be similarly positioned in relation to the braking mechanism andthe make and break contacts H0, H4 so that the wiper blades will be in aparked position when the motor and its associated parts are brought to astop by the action of the brake.

40 Communication between the crank pin I00 and the wiper blades 25 isestablished by a dogleg shaped link I82 which joins the crank pin to apin I84 on the lower end of a walking beam I88 which is mounted on thesupport 28. The reciprocating movement of the walking beam I88 istransmitted by a link I88 to an arm "0 of the wiper blade shaft I12.Similarly, another link I14 joins the-walking beam I88 to an arm "8 ofthe other wiper blade shaft I18.

A terminal block I80, as in Fig. 2, is secured to bosses I82, I84 whichare cast integral with the housing 32. Mounted on the terminal block isan automatic circuit breaker, I88 of the type which re-establishes thecircuit after a cooling period. A resistor I88 is mounted on the side ofthe terminal block I opposite the circuit breaker I88.

Referring to Fig. 10, the speed of the motor 20 is controlled by meansof the two-speed manual switch I38 which may be mounted on the dashboardof the automobile or at any other convenient location. The motor 20 isconnected to. a usual automobile battery I 90 by means of a conductorI82. The automatic circuit breaker I88 is shown as interposed betweenthe battery. I80 and the manual switch I38. The electricfmotor 20 has anarmature circuit I84 and a field. circuit I88.

A parallel low speed circuit through th1e make and break contacts I I 0,I I4 is established through the conductors I 88, 200. In Fig; 10 thisparallel circuit is represented as .broken because the camming surfaceI02 has actuated the'cam follower I04 thus causing the ,contactsll0, II4to separate.

For high speed operation of the motor, the resistor I88 isinterposed inthe field circuit by means of the manual switch I38. When it is desiredto operate the motor in low speed, a circuit is established through aconductor 202 to the field circuit I88 thus cutting out the resistorI88. It is to be understood, of course, that a high speed circuit is notessential, and my windshield wiper can be operated equally well withoutit.

A modification of the coupling which links the armature shaft 40 to theworm gear shaft 44 is shown in Fig. 11. This modification consists of acoupling shaft 208. dog-bone in shape, and having generally sphericalends 208, 2I0, which are slightly flattened 2I2, 2I4. The end 208 isprovided with protruding ears 2I8, '2I8, and the end 2I0 is providedwith similar ears 220, 222. These ears are formed preferably by a simplepinching or pressing operation. The spherical end 208 fits movably inthe bore 52 of the worm gear shaft and the ears 2I8, 2 l8 rest in theaxial slots 54. The ball58 which is press-fitted into the bore 52 of theworm gear shaft 44 serves as a bearing surface for the slightlyflattened spherical end 208 and prevents the ears 2I8, 2I8

from touching the inner ends of the slots 54.

The other end 2I0 of the coupling shaft 208 fits movably in the bore 84of the armature shaft 40 and the ears 220, 222 rest in the axial slots80. In this embodiment a spring 224 abuts the slightly flattened end 2thus holding the coupling securely in place and taking up any end playthat may be present due to variation in the length of the armatureshaft. In order to make certain that the coupling operates smoothly, theedges 226, 228 of the ears 2I6, 2I8 are rounded on the sides which arein contact with the slots. The edges of the ears 220, 222 are likewiserounded. This not only minimizes friction' and prevents binding, butalso allows the coupling a greater degree of side play and thus enablesit to act as a universal joint.

The operation of my windshield wiper and its novel mechanism for parkingthe wiper blades is as follows: When the manual switch l38 is turned toan on position, either high or low, the motor 20 revolves the coupling42 which in turn revolves the worm gear 38 and the worm wheel 38. Thecombined cranking and camming member 98 revolves with the worm wheelshaft 89 and turns the crank pin I00 which is linked to the windshieldwiper blades 25. The crank pin, through the linkage 24, causes the wiperblades to reciprocate in an arc across the windshield as previouslydescribed.

With each revolution of the worm wheel 38, the braking cam I38 and thebrake shoe I48 come into contact with each other. As this contact takesplace, the wiper blades are in a parked position and the crank pin I00is at dead center; (see Fig. 1) therefore at the time when the brakingmembers are together, there is scarcely any movementin the linkage 24,and consequently the linkage imposes noappreciable load upon the motor20. As a result, most of the motive power is available to cause thebraking members to overrideone another.

With each revolution of the worm wheel-shaft 89, the camming surface I02actuates the insulated cam follower I04, thus flexing the spring arm I08and separating the contacts H0, H4. This would break the circuit to themotor 20 were it not for the fact that a parallel circuit through themanual switch I38 has beenestablished.

When the driver desires to turn oi the windshield wiper, he simply turnsthe manualswitch I38 to the "o position. The circuit to the motorthrough the manual switch is thereby broken, but the motor will continueto operate inlow speed until the parallel circuit through the make andbreak contacts H0, H4 is broken by the contact of the camming surfaceI02 with the cam follower I04. When this takes place, the current to themotor is completely out off,

and momentarily thereafter the braking incline I40 of the braking camI38 meets the braking surface I52 of the brake shoe I48. Inasmuch as themotor has ceased to run, the leaf spring I50 will have suflicientrigidity to hold the brake shoe I48 against the braking cam I38 andthere-.

by stop the entire wiper mechanism in its predetermined parked position,as previously described.

It may happenoc-casionally that the moving parts will have suflicientmomentum to carry the flat dwell -I42 on the braking cam I38 past theapex I58 of the brake shoe I40, even though the current to the motor 20is cut oil. This situation is most likely to occur in cases where themanual switch is turned from the "high speed position to the off"position momentarily before the braking cam meets the brake shoe.Consequently a low speed circuit to the motor 20 is not established intime to diminish sufliciently the speed of the moving parts before thebraking takes place; therefore the braking cam and the brake shoe willoverride one another. Simultaneously with the overriding of the brakingmembers, the camming surface I02 releases the cam follower I04 so thatthe contact points' I I0, H8 come together to establish a low speedcircuit to the motor 20. Of course, the next oper-.

ation isv at low speed and the moving parts will not have sufficientmomentum to carry the braking cam I38 past the brake shoe I48 upon. thenext revolution of the worm wheel.

It is to be understood that my invention may assume numerous forms andthat it is not limited to the details illustrated and described here- Iclaim:

1. An electric windshield wiper for a vehicle having a battery, saidwiper having wiper blades,

an electric motor for driving said wiper blades, a

manual switch for connecting said motor with said battery, 2. make andbreak switch operative in a circuit parallel with the circuit controlledby the manual switch, driving mechanism interposed between said motorand said wiper blades, said driving mechanism. comprising incombination. a rotatable element driven by said motor, cranking meansrevolving with the rotatable element, linkage between said crankingmeans and said wiper blades, 2, camming member for operating said makeand break switch, and braking means to stop the windsh eld wipermomentarily after said make and break switch has cut off the current tothe motor, said braking means comprising a braking cam on said rotatableelement, a brake shoe to engage said braking cam and means resilient tourge said brake shoe against said braking cam, said braking camcomprising a braking incline on the portion of the braking cam whichfirst meets the brake shoe, a reverse slope on the side opposite thebraking incline, and a flat dwell between said inciine and said slope,said brake shoe having opposed surfaces complementary to said brakingincline and said reverse slope, said braking means being inoperative tostop the windshield wiper when the motor is under power, but beingopernism interposed between said motor and said wiper blades, saiddriving mechanism comprising in combination a worm gear driven by saidmotor, a worm wheel driven by said worm gear, cranking means connectingsaid driving mechanism with said wiper blades, camming means foroperating said make and break switch, and a friction brake to stop theentire windshield wiper assembly momentarily after said make and breakswitch has cut oil the current to the motor, said frictio'n brakecomprising a braking cam on said worm wheel, a stationary brake shoe toengage said braking cam, and means resilient to urge said brake shoeagainst said braking cam, said braking cam comprising a braking inclineon the side of the braking cam which first meets the brake shoe, areverse slope on the side opposite the braking incline, and a flat dwellbetween said incline and said slope, said brake shoe having a brakingsurface complementary to said braking incline and a reverse inclinecomplementary to said reverse slope, said friction brake beinginoperative to stop the windshield wiper when the motor is under power,but being operative to stop the windshield'wiper when the power to themotor is cut off, said friction brake being positioned in relation tosaid cranking means and said camming member to stop the wiper blades ina predetermined location. 3. An electric windshield wiper for a vehiclehaving a battery, said wiper having wiper blades,

an electric motor for driving said wiper blades,

a manual switch for connecting said motor with said battery, a make andbreak switch operative in a circuit parallel with the circuit controlledby the manual switch, driving mechanism for the wiper blades interposedbetween said motor and said wiper blades, ,said driving mechanismcomprising a worm gear driven by said motor, a worm wheel driven by thewonn gear, a shaft for the worm wheel, a combination member on saidshaft, said combination member having camming means for operating saidmake and break switch and cranking means coupled to said wiper blades,and braking means to stop said worm wheel momentarily after said makeand break switch has cut oil the current to the motor, said brakingmeans comprising a braking cam on said worm wheel,

a stationary brake shoe, and means resilient to urge said brake shoeagainst said braking cam, said braking means being positioned inrelation to said cranking means and said camming means to stop thewiping means in a predetermined location.

4. In an electric windshield wiper, the combination of wiper blades, 9.motor for driving said blades, driving mechanism interposed between -aworm wheel driven by the worm gear, cranking means revolving with saidworm wheel, linkage between said cranking means and said wiper blades,and braking means cooperating withsaid driving mechanism to stop thewiper blades in a predetermined position, said braking means comprisinga braking cam on said worm wheel, a stationary brake shoe, and means tourge said brake shoe against said braking cam with each revolution ofsaid worm wheel, said braking cam comprising a braking incline, aretreating incline, and a flat dwell between said inclines, said brakeshoe having opposed surfaces complementary to said inclines of thebraking cam, said braking means being inoperative to stop the wiperblades when the motor is under power, but being operative to stop thewiper blades when the power to the motor is cut oil.

5. An electric windshield wiper for a vehicle having a battery, saidwindshield wiper having wiper blades, an electric motor for driving saidwiper blades, a manual switch for connecting said motor with saidbattery, a make and break switch operative in a circuit parallel withthe-circuit controlled by the manual switch, driving mechanisminterposed between said motor and said wiper blades, said drivingmechanism comprising in combination a worm gear, a worm wheel driven bysaid worm gear, a shaft for the worm wheel, a combination member on saidshaft, said combination member having camming means for operating saidmake and break switch and a crank pin coupled to said wiper blades, andbraking means positioned in relation to said crank pin and said cammingmeans to stop said wiper blades in a predetermined position, saidbraking means comprising a braking cam on the side of said worm wheel, astationary brake shoe, and a'leaf spring to urge said brake shoe againstsaid braking cam with each revolution of said worm wheel, said leafspring. having an aperture therein in order that said worm wheel shaftmay extend therethrough, said braking cam comprising a braking incline,a. retreating incline, and a fiat dwell between said inclines, said brakshoe having a braking surface complementary to said brak ing incline andan opposed reverse incline complementary to said retreating incline,said braking means being inoperative to stop the wiper blades when themotor is under power but being operative to stop the wiper blades whenthe powei to the motor is cut oil.

6. An electric windshield wiper of the class described having wiperblades, a motor for driving said blades, driving mechanism interposedbetween said motor and said blades, said driving mechanism comprising aworm gear having a recess at one end, said end receiving the majority ofthe thrust exerted by said worm gear, a ball pressed into said recess, athrust plate providing a bearing surface for said ball, a worm wheeldriven by the worm gear, cranking means revolving with said worm wheel,linkage between said cranking means and said wiper blades, and brakingmeans co-operating with said driving mechanism to stop the-wiper bladesin a predetermined position, said braking means comprising a braking camon said worm wheel, a stationary brake shoe, and means to urge saidbrake shoe against said braking cam with each revolutionof said wormwheel, said braking cam comprising a braking incline, a retreatingincline, and a flat dwell be- '7. In a windshield wiper of the classdescribed, the combination of a wiper blade, a power driven motor foroperating said blade, a rotatable element driven by said motor andcoupled to the wiper blade to reciprocate it, a

friction brake being positioned in relation to said cranking means andsaid camming member to hump on said rotatable element. a stationarybrake shoe adapted to engage said hump with each revolution of therotatable element, said brake shoe being inoperative to stop therotatable element when the motor is under power but being operative tostop th rotatable element stop the wiper blades in a predeterminedlocation, said friction brake being engageable for each cycle ofoperation of said wiper blades and being operative to stop said wiperblades when the circuit to the motor is broken, but being inoperative tostop said wiper blades when the motor is running.

10. An electric windshield wiper for a vehicle having a battery, saidwiper having wiper blades, an electric motor for driving said wiperblades through a given cycle of operation, a manual switch forconnecting said motor with said battery, a make and break switchoperative in a circuit parallel with the circuit controlled by the whenthe power to themotor is cut off, said hump and said brake shoe beingrelatively located to stop the wiper blade in a predetermined position.

8. An electric windshield wiper for a vehicle 'having a battery, saidwiper comprising wiper blades, an electric motor for driving saidblades, 2. manual switch for connecting said motor with said battery, amake and break switch operative in a circuit parallel with the circuitcontrolled by the manual switch, driving mechanism interposed betweensaid motor and said wiper blades, said driving mechanism comprising. incombinaton a rotatable element driven by said motor, cranking meansrevolving with the rotatable element, linkage between said crankingmeans and said wiper blades, a camming member for openting said make andbreak switch, and braking means to engage said rotatable elementmomentarily after said mak and break switch has cut on the current tothe motor, said braking means 'being positioned in relation to saidcranking means and said camming member-to stop the wiper blades in apredetermined location.

9. In an electric windshield wiperior a vehicle having a battery, thecombination of wiper blades, a motor for driving said blades through agiven cycle of operation, a manual switch for connecting said motor withsaid battery, 8. make' and break switch operative in a circuit parallelwith the circuit controlled by the manual switch, drivingmechanism-interposed between said motor and said wiper blades, saiddriving mechanism comprising a rotatable element driven by said motor,cranking means coupled to said rotatable element, a linkage connectingsaid cranking means with said-wiper blades, a camming member foroperatingfsaid make and br electric vmotor for said wiper blade,

manual switch, driving mechanism interposed between said motor and saidwiper' blades, said driving mechanism comprising in combination arotatable element driven by said motor; cranking means revolving withsaid rotatable element, linkage between said cranking means and saidwiper blades, a camming member for operating said make and break switch,and braking means to stop said windshield wiper in a predeterminedmomentarily after said make parked position has cut off the current tothe and break switch motor, said braking means being activated for 11.In an electric windshield wiper of th class I described, the combinationof a wiperblade, an driving said wiper blade through a predeterminedcycle of operation, switch means for connecting said electric motor witha source of electrical energy, driving mechanism interposed between saidelectric motor and said wiper blade, and-a friction brake ior stoppingsaid wiper blade in a predetermined parked position, said friction brakeincluding a first part movable with said driving mechanism and arelsecond part, said brake parts for each cycle of movement oi saidelectric motor exerting atively stationary being engageable suflicientforce when connected with said source switch, and a friction brake forstopping said the circuit bewiper blades momentarily after said tweensaid battery and said motor is broken,

nected from said source of electrical energy to overcome the frictionalresistance of said brake, said brake being effective to stop said wiperbladein said parked position only when said electrical motor is disconofelectrical energy. JOHN B. WHITIED.

